Pressing the select button twice on the now playing screen allows you to view/set a song's rating. The first press allows you to "scrub" through the song with the scroll wheel. The dock connection noise comes from the iPod itself.

The first poster used the words, "I think" and, "probably", in their answer. I thought I would clarify by pointing out that it was two presses of the select button and confirm that the sound did indeed come from the iPod.